Barbara J. Bain, MB BS, FRACP, FRCPath, AM, is Professor of Diagnostic Haematology, St Mary's Hospital Campus, Imperial College Faculty of Medicine and Consultant Haematologist, St Mary's Hospital, London, UK. Mike Leach, MB ChB, FRCP, FRCPath is Consultant Haematologist and Honorary Senior Lecturer, Haematology Laboratories and West of Scotland Cancer Centre, Gartnavel General Hospital, Glasgow, UK.